Rajon Rondo stole an inbounds pass in the closing nine seconds, but he dribbled to nowhere and the Celtics never got a shot off. Paul Pierce missed a layup and chucked an airball in the final minute. The Celtics lost track of the foul situation and did not have a timeout after Rondo stole the ball.

“I didn’t like our execution down the stretch,’’ said Celtics coach Doc Rivers. “Overall, they played harder. They played better.’’

So now the series returns to Boston, where the Jurassic Park Green Teamers will try to eliminate the Hawks Thursday night at the Garden. Boston’s 3-1 series lead is now 3-2. These Celtics can’t seem to do anything the easy way, but no Celtics team ever has coughed up a 3-1 series lead.

“They’ve got confidence and momentum,’’ said Pierce with a sigh. “We have to go home and get the job done.’’

Ugh. More uglyball. The Celtics couldn’t hold an 11-point lead in Atlanta in Game 2. They had to go into overtime to win Game 3 at home against a depleted Hawks team that was ready to bring back Sly Williams. The blowout Sunday seemed like Atlanta’s concession speech, but Tuesday night the Celtics couldn’t close it out.

The Celtics need to end it Thursday. They do not want to come back to Atlanta for Game 7 Saturday night. You know what Kevin Millar says about Game 7s.

I am not worried. There is no way the Celtics could lose three straight to these guys. Impossible. I guarantee you no team has lost three straight after taking a 37-point lead in Game 4.

The Celtics are going to the next round and they are going to play the Philadelphia 76ers. I haven’t been this sure about anything in sports since the Red Sox led the Orioles and the Yankees led the Rays, 7-0, on that final night last September.

Excuse me, while I look ahead.

Celtics-Sixers. Can’t wait.

This is the kind of thinking Bill Belichick hates more than injury disclosures. Hoodie breaks out in hives when he hears us discussing the upcoming Patriots schedule, and projecting a 13-3 record with losses to the Ravens, Jets, and Niners.

Sorry, but looking ahead prematurely is what we do. We count the chickens before they are hatched. It has to be done. I’d like to start talking about Celtics vs. Heat in the conference finals. Like the 2011 Patriots, the Celtics are beneficiaries of some nice breaks at the start of the playoffs. The Patriots drew a horrible Denver team for the first round. The Celtics got the Atlanta Tomato Cans. They need to take advantage of their good fortune and put the Hawks to bed.

There will be some brief hysteria about the Celtics not being able to contend with any legitimate big man (hello, Al Horford), but let’s try to remember the way the Celtics dominated Game 4.

I know, I know. It’s not over till it’s over. But it’s hard to take the Hawks seriously. They got a big boost from Horford in Game 5, but these Celtics aren’t going to lose to the Hawks. The Hawks play in a gym that is one-third empty at the start of an elimination playoff game. They pipe noise into the arena to drown out the Celtics fans. The fans leave early unless the game is tied in the final minute. And you cannot blame them. No Atlanta Hawk team has ever done . . . anything.

But the Celtics need to be careful. A choke-hold can turn into a choke.

Rivers keeps telling us that the playoffs are about mental toughness. He has Hall of Famers and champions on his roster. They did not appear mentally tough in Game 5.

“I tried to make a play, but got caught on the baseline,’’ Rondo said when asked about dribbling out the clock, then turning the ball over at the buzzer. “I just didn’t come up with the shot.’’

“We definitely squandered away an opportunity,’’ said Pierce.

All true. But does anyone really think they can lose three straight to the Atlanta Hawks?